Method of operating a hydrodynamic compression tool and hydrodynamic compression tool

ABSTRACT

A hydrodynamic compression tool comprises a motor which actuates a hydrodynamic group suitable to increase the pressure of a hydraulic fluid acting on an actuation piston connected to jaws, an electronic control system connected to the electric motor and to a user operating member for the actuation of the electric motor. An identification detector in connection with the control circuit detects an identification characteristic of the jaws or inserts housed in the jaws or of an object to be compressed or cut.

RELATED APPLICATIONS

This is a continuation of application Ser. No. 15/312,404, filed Nov.18, 2016, which is a 371 of PCT/IB2015/054589, filed Jun. 18, 2015,which claims priority to Italian Application No. MI2014A001240, filedJul. 7, 2014, each of which is incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a method for operating a hydrodynamiccompression and/or cutting tool as well as a hydrodynamic compressiontool configured to implement such method.

2. Description of the Related Art

To perform specific connection operations, such as the compression ofconnectors around electrical cables or hydraulic pipes, the compressionof rivets, or cutting operations, such as cutting electrical cablesduring the installation and maintenance of electrical installations,hydrodynamic compression and/or cutting tools are often used.

Such tools usually comprise an electric motor powered by a battery and ahydraulic pump which causes an increase in pressure of a hydraulic fluidacting on a piston to move the latter against the force of a pressurespring. The piston is in turn connected to a movable jaw so as to moveit during the compression operation, towards a fixed jaw of the tool.The jaws can be shaped and/or fitted with interchangeable accessories insuch a way as to adapt it to a particular object, e.g. an electricalcontact to be compressed or a metal bar to be cut.

Since compression tools are used very often in outdoor environments,such as along railway lines remote from buildings with a connection tothe mains electricity, they need their own electrical power source,namely a portable storage battery built into or applied to the tool.Such battery provides a limited amount of electrical energy whichdetermines its autonomy, i.e. the number of compression/cuttingoperations which can be performed by the tool without having to replacethe battery. A further requirement is due to the fact that most of thetime compression operations, in particular those aimed at makingconnections between connectors and/or electrical cables are hampered byextremely restricted space conditions, such as in an electrical cabin oron an electrical wiring line that combines a large number of cables veryclose together. It is therefore essential for compression tools to be acompact size. A third requirement is to be able to perform thecompression and cutting operations with appropriate speed in order toreduce the time required to perform the work. A fourth requirement notmet so far is to increase the fatigue life of the mechanical componentsof the tool, despite their small size and cyclical stresses.

The purpose of the present invention is therefore to provide a method ofoperating a hydrodynamic compression tool and a hydrodynamic compressiontool with characteristics such as to overcome the problems mentionedwith reference to the prior art.

One particular purpose of the invention is to provide a method and ahydrodynamic compression tool which allows an adjustment of the maximumcompression force, electrical power absorption and duration of thehydrodynamic pressure to the size and compression-resistance of anobject to be compressed.

In the context of the present invention, the inventors have consideredthat the compression tools of the prior art, in order to ensurecompletion of the compression of electrical or hydraulic connectors andto prevent damage due to excessive stress, end the compression phaseupon reaching a maximum calibration force, for example of 60 kN. This isachieved for example either by a pressure relief valve connected to thehydrodynamic group and calibrated in such a way as to limit thehydraulic pressure acting on the piston to a maximum pressure whichcorresponds to the maximum calibration force.

The user thus has the certainty of always having applied a sufficientforce to complete the compression of electrical or hydraulic connectors,regardless of their size or resistance to compression. In fact, thecompression tool is usually designed to be able to compress connectorsof a predetermined size range, e.g. connectors for electric cables withtransversal cross-sections from 6 mm² to 240 mm², and the maximumcalibration force is set to compress the largest size connector.

If the compression tool is used as a cutting tool, the termination ofthe compression phase upon reaching the maximum calibration forceprotects the mechanical components of the tool from damage due toexcessive stress.

However, except for very rare cases, compression tools are used tocompress very different sized connectors and very often smaller than themaximum size for which it is necessary to apply the maximum calibrationforce.

As a result, after the complete compression of a small connector, thejaws of the tool are tightened against each other until the maximumcalibration force is reached which determines the end of the compressioncycle. Such further stress of the jaws does not contribute to thecompression of the connector but instead entails a peak power absorptionand mechanical stress, the reduction of which is the starting point forachieving the objectives of the invention.

SUMMARY OF THE INVENTION

A method for operating a hydrodynamic compression tool is thus proposed,said tool comprising:

an electric motor powered by a battery or from the mains;

a hydrodynamic group operable by the electric motor and suitable toimplement, in response to the movement of the motor, an increase inpressure of a hydraulic fluid acting on an actuation piston to move theactuation piston;

two jaws connected to the housing so as to be reciprocally mobile, ofwhich at least one mobile jaw is connected to the actuation piston sothat, in response to the movement of the actuation piston, the jawsperform a relative movement between an open position and a closedposition to perform the compression or cutting,

wherein in the open position the jaws are spaced apart so as toaccommodate the object to be compressed or to be cut and, in the closedposition, the jaws are moved in close approximation until getting indirect contact (in particular against each other) such as to prevent afurther approximation towards each other,wherein the method comprises the steps of:

approximating the jaws towards each other by actuating the electricmotor,

monitoring the reaching of the closed position by means of a sensor,

interrupting the actuation of the electric motor depending on a sensorsignal which confirms that the closed position has been reached.

This way it is possible to stop the electric motor and thepressurisation of the hydraulic fluid upon completion of the compressionof an object, e.g. an electric or hydraulic connector, withoutcontinuing the compression cycle until the maximum calibration force hasbeen reached, thereby saving electric energy and reducing the peakstress of the mechanical components of the tool.

Hence, an increased fatigue life duration, an increase in the number ofcompressions which can be performed with one recharging of the battery,a reduction of the time needed to complete the single compression orcutting, and a possible reduction in the size of the mechanicalcomponents of the tool for the same fatigue life is achieved.

The purpose of the invention is also achieved by a hydrodynamiccompression tool, comprising:

an electric motor powered by a battery or from the mains,

a hydrodynamic group operable by the electric motor and suitable, inresponse to the movement of the motor, to increase the pressure of ahydraulic fluid acting on an actuation piston to move the actuationpiston;

two jaws connected to the housing so as to be reciprocally mobile, ofwhich at least one mobile jaw is connected to the actuation piston sothat, in response to the movement of the actuation piston, the jawsperform a relative movement between an open position and a closedposition to perform the compression or cutting,

wherein in the open position the jaws are spaced apart so as to be ableto accommodate the object to be compressed or to be cut and, in theclosed position, the jaws are approximated towards each other untilgetting in direct contact (in particular against each other) such as toprevent a further mutual approximation thereof,

an electronic control system connected to the electric motor and with auser operating mechanism (push-button) to operate the electric motor,

wherein the control system comprises a monitoring device which monitorsreaching of the closed position and, upon achievement of the closedposition, generates a confirmation signal,and in that the control system interrupts the actuation of the electricmotor automatically in dependency from the confirmation signal that theclosed position has been reached.

BRIEF DESCRIPTION OF THE DRAWINGS

For a clearer understanding of the invention and its advantages some ofits embodiments, made by way of non-limiting examples, will be describedbelow with reference to the appended drawings, wherein:

FIG. 1 is a pressure-time (or pressure-number of pump cycles) diagram ofan “idle” compression (no object to be compressed inserted between thejaws) of a compression tool of the prior art with limitation of thepressure by means of a maximum pressure relief valve which switches whenit reaches the maximum calibration pressure Pmax.

FIG. 2 is a pressure-time (or pressure-number of pump cycles) diagram ofan “idle” compression (no object to be compressed inserted between thejaws) of a compression tool according to the invention which implementsthe method of the invention.

FIG. 3 is a pressure-time (or pressure-number of pump cycles) diagram ofthe compression of a connector or object of large dimensions whichrequires nearly the maximum calibration force, using a compression toolof the prior art with limitation of the pressure by means of a maximumpressure relief valve which switches when it reaches the maximumcalibration pressure Pmax.

FIG. 4 is a pressure-time (or pressure-number of pump cycles) diagram ofthe compression of a connector or object of very large dimensions whichrequires practically the maximum calibration force, using a compressiontool according to the invention that implements the method of theinvention.

FIG. 5 is a pressure-time (or pressure-number of pump cycles) diagram ofthe compression of an object of small-medium dimensions which does notrequire the maximum calibration force, by means of a compression tool ofthe prior art with limitation of the pressure using a pressure reliefvalve which switches when it reaches the maximum calibration pressurePmax.

FIG. 6 is a pressure-time (or pressure-number of pump cycles) diagram ofthe compression of an object of small-medium dimensions which does notrequire the maximum calibration force, using a compression toolaccording to the invention that implements the method of the invention.

FIG. 7 is a perspective view of an electrohydraulic compression orcutting tool according to an embodiment of the invention, fitted with acompression head suitable to receive inserts or interchangeable jawdies.

FIG. 7A shows a sequence of movement of the compression head of the toolshown in FIG. 7.

FIGS. 8 and 9 show hydrodynamic compression tools according toembodiments of the invention fitted with translatable or rotatable jawsfor the compression of electrical and/or hydraulic connectors.

FIGS. 10, 11, 12 are schematic diagrams of hydrodynamic compressiontools and their control systems according to embodiments of theinvention.

FIG. 13 shows a compression tool in which the compression head isdistanced from the pumping group and connected to it by means of aflexible pressure hose.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIGS. 7-12, a hydrodynamic compression tool and/orcutting tool is globally denoted by reference numeral 1. The tool 1comprises a housing 2 with a grip shaped portion 3 and a couplingportion 4 for the (preferably snap-) connection of a replaceable andrechargeable storage battery 5. The housing 2 houses an electric motor 6powered by the storage battery 5 via a power supply and control circuitfitted with a switch on which acts a manual actuation pushbutton 7placed in proximity of the handle 3.

A transformation mechanism 8, such as a crankshaft or cam shaft, isplaced in the housing 2 and connected to the drive shaft of the motor 6so as to transform the rotary movement of the drive shaft into cyclicalor reciprocating movement, for example translational. A hydraulic pump11, also housed in the housing 2, is connected to the transformationmechanism 8 and is suitable, in response to the cyclical orreciprocating movement of the transformation mechanism 8, to increasethe pressure of a pressure fluid acting on an actuation piston 12 so asto move the actuation piston 12 along a piston stroke.

The tool 1 further comprises a fixed jaw 13 rigidly connected to thehousing 2 and placed at a front end of the tool, as well as a mobile jaw14 supported in the housing so as to be able to slide in relation to thefixed jaw 13. The mobile jaw 14 is connected to the actuation piston 12so that, in response to the movement of the actuation piston 12, it ismoved towards the fixed jaw 13 from an open position to a closedposition, to perform the or compression or cutting operation.

In the open position the jaws 13, 14 are spaced apart to accommodate theobject to be compressed or cut and, in the closed position, the jaws 13,14 are moved close together and in direct contact (in particularabutting against each other) such as to prevent a approximating movementthereof.

A return spring 15 acts between the fixed jaw and the actuation piston12, so as to urge the latter elastically into the rest position and themobile jaw 14 into the open position away from the fixed jaw 13.

According to one embodiment, the hydraulic pump 11 comprises a tank 16,a cylinder-pumping piston group, a cylinder-actuation piston group and apressure relief valve 17.

The cylinder-pumping piston group may comprise a pumping cylinder with asuction opening connected to the tank 16 by means of a check valve thatallows the flow of hydraulic oil from the tank into the pumping cylinder16 and an output opening connected to an actuation cylinder 10 of thecylinder-actuation piston group by means of a check valve that allowsthe flow of hydraulic oil from the pumping cylinder into the actuationcylinder 10. In the pumping cylinder a pumping piston may be housedcoupled so as to move together with an oscillating body (for example anelbow portion) of the transformation mechanism 8.

The cylinder-actuation piston group comprises the actuation piston 12connected to the mobile jaw 14 and placed in the actuation cylinder 10.

The pressure relief valve 17 is placed in a return duct for the fluidwhich return duct connects the actuation cylinder 10 to the tank 16(FIGS. 10, 11, 12).

This way, the reciprocating translatory movement of the transformationmechanism 8 generated by the rotating movement of the drive shaft causesan oscillating translatory movement of the pumping piston which pumpsthe pressure liquid from the tank 16 into the actuation cylinder 10 tomove the actuation piston 12 forward and, together therewith, the mobilejaw 14 from the open position to the closed position until the actuationcylinder 10 reaches a pre-determined maximum calibration pressure. Uponreaching the maximum calibration pressure, the pressure relief valve 17automatically opens the return duct 21 of the fluid to drain thepressure liquid from the actuation cylinder 10 into the tank 16.

According to one aspect of the invention, the method of operating thetool 1 comprises the steps of:

moving the jaws 13, 14 towards each other by actuating the electricmotor 6

monitoring the reaching of the closed position using a sensor 22, 23, 24and an electronic control circuit 9 connected to the sensor 22, 23, 24and to the electric motor 6,

interrupting the actuation of the electric motor 6 depending on a signalby sensor 22, 23, 24 which confirms that the closed position of the jaws13, 14 has been reached.

According to one embodiment (FIG. 10), the monitoring of the reachingthe closed position comprises:

detecting at predetermined time intervals (or predetermined intervals ofthe pumping cycles of the hydraulic pump 11) the pressure of thehydraulic fluid acting on the actuation piston 12, using a pressuresensor 22 connected to the electronic control circuit 9,

using the electronic control circuit 9, calculating a pressuredifference measured at the beginning and at the end of each of saidpredetermined time intervals (or predetermined intervals of the pumpingcycles) and comparing the calculated pressure difference with anreference value indicative for the closed position of the jaws 13, 14.

The increase in pressure per unit of time Δp/Δt or per pumping cycleΔp/n_(p) is indicative of the derivative of the pressure function p=f(t) over time with the hydraulic pump 11 switched on and, therefore, therigidity countering a further movement towards each other of the jaws13, 14, and the reference value of Δp_ref/Δt represents the rigidity ofthe system when the jaws 13, 14 are in direct contact with each otherand any further approximation movement thereof is prevented.

According to a further embodiment (FIG. 11), the monitoring of reachingthe closed position comprises:

detecting at predetermined time intervals Δt (or at predeterminedintervals of the pumping cycles n_(p)) an electrical quantity indicativefor the power absorbed by the motor, using an electric sensor 23connected to the electronic control circuit 9,

using the electronic control circuit 9, calculating a difference betweenthe electrical quantity measured at the beginning and at the end of eachof said predetermined time intervals Δt (or predetermined intervals ofthe pumping cycles n_(p)) and comparing the difference of the calculatedelectrical quantity with a reference value indicative for the closedposition of the jaws 13, 14.

For example, in the case of a direct current motor 6 with knownimpedance, the electric current I absorbed by the motor 6 can be used asan electrical quantity indicative of the power absorbed by the motor 6and measured using a current sensor 23.

In this case, the change in the power absorbed by the motor 6 per unitof time Δt, or per pumping cycle n_(p) indicates the stiffness opposinga further approximation movement of the jaws 13, 14 and the referencevalue represents the stiffness of the system when the jaws 13, 14 are indirect contact with each other and prevent any further movement towardseach other.

According to a further embodiment (FIG. 12), the monitoring of reachingthe closed position comprises:

detecting at predetermined time intervals Δt (or at predeterminedintervals of pumping cycles n_(p)) a distance D between two referencepoints 25, 26, of the two jaws 13 14, using a distance sensor 24, suchas an optical sensor or a linear transducer, connected to the electroniccontrol circuit 9,

using the electronic control circuit 9, calculating a difference ΔD ofthe distance D measured at the beginning and at the end of each of saidpredetermined time intervals Δt (or predetermined intervals of thepumping cycles n_(p)) and comparing the calculated difference of thedistance D with a reference value ΔDref indicative for the closedposition of the jaws 13, 14.

In this case, the change ΔD in the distance D between the two referencepoints 25, 26 per unit of time Δt, or per pumping cycle n_(p) indicatesin inverse relation the stiffness opposing a further movement towardseach other of the jaws 13, 14 and the reference value ΔDref representsthe stiffness of the system when the jaws 13, 14 are in direct contactwith each other and prevent any further movement towards each other.

According to a further embodiment of the invention (FIG. 12), themonitoring of reaching the closed position comprises:

detecting at predetermined time intervals Δt (or at predeterminedintervals of pumping cycles n_(p)) a distance D between two referencepoints 25, 26, of the two jaws, 13 14, using a distance sensor 24, suchas an optical sensor or a linear transducer, connected to the electroniccontrol circuit 9,

using the electronic control circuit 9, comparing the measured distanceD with a reference value Dref indicative for the closed position of thejaws 13, 14.

In this case, the monitoring of reaching the closed position does nottake place by monitoring the structural response of the tool 1 to thepumping of hydraulic fluid, but directly.

In this embodiment steps may also be provided for the identification ofa jaw type or die or insert type for interchangeable jaws (to adapt thetool 1 to the shape of the object to be compressed or cut) and todetermine the reference value according to the type of jaw or type ofjaw insert identified.

This step of the method may be performed automatically, for example bymeans of an identification detector 27 connected to the control circuit9 and suitable to detect an identifying feature of the jaws 13, 14 or ofthe inserts for jaws 13′, 14′ (FIG. 7A), for example:

a shape feature of a mechanical interface of the jaw or the insert,

an optical or chromatic feature of an optical interface of the jaw orthe insert,

a magnetic feature of a magnetic interface of the jaw or the insert,

an electrical feature of an electric interface of the jaw or the insert,

a signal of a radio frequency identification tag (RFID tags) of the jawor the insert,

and subsequent determination of the reference value Dref according tothe identified type of jaw or jaw insert.

Similarly, provision may be made to identify the type of the object tocompress or cut and possibly to perform switching off of the electricmotor or other functions of the tool at least also depending on the typeof object identified.

For the identification of the object to be compressed or cut an objectidentification detector may be provided for which can be created andconfigured as the identification detector 27 described above.Alternatively, the object identification detector may comprise aposition sensor configured to detect a position of the actuation piston,wherein the electronic control circuit is in signal connection with thepressure sensor, with the position sensor and with the electric motor,and configured to identify an object engaged by the jaws (13, 14)depending on the hydraulic fluid pressure detected by the pressuresensor and on the position of the actuation piston detected by theposition sensor during actuation of the electric motor. Suchidentification of the object may take place automatically for example bymeans of the following steps:

identifying, on the basis of the monitored pressure, an engagementmoment in which the jaws engage the object placed between them and inwhich the compression of the object commences,

detecting a compression starting position of the actuation piston at themoment of engagement,

identifying the object engaged by the jaws depending on the detectedcompression starting position.

According to a further embodiment (not shown), the monitoring ofreaching the closed position comprises:

placing a switch, e.g. electrical or optical, at the jaws 13, 14 so thatthe reaching the closed position due to an approximation movement of thejaws 13, 14 causes a determined switching process of the switch,

detecting said switching process by means of the control circuit 9connected to the switch.

Advantageously, the step of monitoring the reaching the closed positionis carried out automatically and the electronic control circuit 9automatically switches off the electric motor 6 when the closed positionof the jaws 13, 14 is reached.

FIGS. 1 to 6 show the technical effect of the method of operating thecompression tool 1 compared to the prior art.

In the case of an “idle” compression of a tool of the prior art (FIG.1), during the approximation movement of the jaws an initial pressure P1occurs required to overcome the friction, inertia and (if provided for)the elastic return force of a return spring acting on the piston. Afterthe jaws or jaw dies reach the closed position and come into contactwith each other, in the moment C2 shown on the t-axis, the hydraulic oilpressure acting on the piston rises rapidly and each step of thegradient ramp represents a pump cycle. If the compression head of thetool and the mechanical connections with the hydrodynamic group wereinfinitely rigid, the pressure would rise vertically up to infinity atthe first pump cycle after reaching the closed position of the jaws. Thepressure increase of the hydraulic fluid stops when it reaches themaximum pressure Pmax in response to the opening of the maximum pressurerelief valve connected to the cylinder of the hydrodynamic group, in themoment Cmax indicated on the t-axis. The area under the curve p betweenthe points C2 and Cmax on the t-axis represents the mechanical workperformed and the electric energy needlessly dissipated after reachingthe closed position of the jaws until the pressure relief valve trips.

In the case of an “idle” compression of a tool according to theinvention which implements the method of the invention (FIG. 2), duringthe approximation movement of the jaws the above initial pressure P1occurs. After the jaws or jaw dies reach the closed position and comeinto contact with each other, as indicated on the t-axis in the momentC2, the hydraulic oil pressure acting on the piston starts to riserapidly only until the electric motor and hydraulic pump are turned offin response to the signal confirming that the closed position has beenreached. Consequently, the pressure increase of the hydraulic fluidstops long before reaching the maximum pressure Pmax, therebysignificantly reducing the electric energy consumption for thecompletion of the compression and the peak mechanical stress of thecompression head of the tool 1.

In the case of compression of a connector or an object having very largedimensions which requires almost the maximum calibration force, using atool of the prior art (FIG. 3), during the approximation movement of thejaws the above initial pressure P1 occurs. After the jaws or jaw insertsreach and engage the object to be compressed, in the moment C1 indicatedon the t-axis, the hydraulic oil pressure acting on the piston risesmoderately initially because of the plastic yielding of the object.Gradually as the object is compressed and its stiffness increases, thepressure increase at every pump cycle increases until the maximumcalibration pressure is reached which occurs approximately coincidingwith the reaching of the closed position of the jaws, in the moment C2indicated on the t-axis. The pressure increase of the hydraulic fluidstops when it reaches the maximum pressure Pmax and the pressure fallsin response to the opening of the pressure relief valve connected to thecylinder of the hydrodynamic group, in the moment Cmax indicated on thet-axis

In the case of compression of a connector or object of very largedimensions that requires almost the maximum calibration force, using thetool according to the invention (FIG. 4), the time-pressure trend, up tothe intervention of the pressure sensor (Cmax), is almost identical tothat shown in FIG. 3, since the compression tool must apply the maximumforce available and, in this situation, there are no margins for savingsof electric energy or for a reduction of the peak stress of themechanical components of the tool.

Depending on the ratio of the maximum calibration force and the forceactually required to reach the closed position of the jaws, thetermination of the compression cycle occurs in this case through theswitching of the pressure relief valve or through electrical motorshutdown in response to the confirmation signal of the closed positionhaving been reached and specifically through the first of the two eventsto occur.

In the case of compression of an object that does not require themaximum calibration force, using a tool of the prior art (FIG. 5),during the approximation movement of the jaws the above initial pressureP1 occurs. After the jaws or jaw inserts reach and engage the object tobe compressed, in the moment C1 indicated on the t-axis, the hydraulicoil pressure acting on the piston rises moderately initially because ofthe plastic yielding of the object. Gradually as the object iscompressed and its stiffness increases, the pressure increase at everypump cycle increases until the closed position of the jaws is reached,in which the jaws get into contact with each other, in the moment C2indicated on the t-axis. At this point, the pressure of the hydraulicfluid acting on the piston rises rapidly and stops when it reaches themaximum pressure Pmax in response to the opening of the pressure reliefvalve connected to the cylinder of the hydrodynamic group, in the momentCmax indicated on the t-axis. The area under the curve p between thepoints C2 and Cmax on the t-axis represents the mechanical workperformed and the electric energy needlessly dissipated after reachingthe closed position of the jaws until the pressure relief valveswitches.

In the case of compression of an object that does not require themaximum calibration force, using a tool according to the invention whichimplements the method of the invention (FIG. 6), during theapproximation movement of the jaws the above initial pressure P1 occurs.After the jaws or jaw inserts reach and engage the object to becompressed, in the moment C1 indicated on the t-axis, the hydraulic oilpressure acting on the piston rises moderately initially because of theplastic yielding of the object. Gradually as the object is compressedand its rigidity increases, the pressure increase at every pump cycleincreases until the closed position, in which the jaws get in contact toeach other, is reached, in the moment C2 indicated on the t-axis. Atthis point the hydraulic oil pressure acting on the piston starts torise rapidly, due to the completion of the plastic deformation of theconnector, only until shutdown of the electric motor, in response to theconfirmation signal of the closed position having been reached.Consequently, the increase in pressure of the hydraulic fluid stops longbefore reaching the maximum pressure Pmax, significantly reducing theelectric energy consumption and the peak mechanical stresses of thecompression head of the tool.

For the implementation of the method described so far the compression orcutting tool 1 may comprise one or more of the aforesaid:

pressure sensors 22,

electrical quantity sensors, in particular current sensors 23,

distance sensors 24,

switches, e.g. electrical or optical,

sensors 27 for the identification of the jaws and/or jaw inserts,

devices for the identification of the object to be compressed or cut,connected to the electronic control circuit 9, forming together amonitoring device that monitors the reaching of the closed position ofthe jaws 13, 14 and which, upon reaching the closed position, generatesthe confirmation signal, and wherein the electronic control circuit 9 isconfigured to stop the actuation of the electric motor 6 automaticallyupon reaching the closed position and depending on the confirmationsignal.

Depending on the embodiment, the sensor 22, 23, 24 on board the tool 1is configured to perform the functions described above with reference tomethod and not repeated here for brevity's sake.

The electronic control circuit 9 is configured to process the signalscoming from the sensor 22, 23, 24 and to control the electric motor 6 inaccordance with the method described above.

The control circuit 9 comprises a processing unit (CPU), a memory(internal or external) associated with processing unit (CPU), acommunication interface associated with the processing units (CPU) andsuitable to receive signals (pressure, current, position, connector orinsert types) from the sensor 22, 23, 24, 27 and to transmit controlsignals to the electric motor 6. The control circuit 9 further comprisesa computer program loaded in the memory and configured to perform theprocessing of signals and the operations needed to implement the methodof operating the tool 1. The control circuit 9 is connected to thebattery 5 when the battery 5 is coupled to the tool 1, and could alsohave its own battery possibly suitable to be charged when the controlcircuit 9 is connected to the battery 5.

According to an embodiment, the tool 1 comprises a user interface 19,such as a keyboard, connected to the control circuit 9, which allows theuser to select the function with automatic shutdown of the motor 6 uponreaching the closed position of the jaws 13, 14 or, alternatively,traditional operation reaching the maximum calibration pressure.

The tool 1 further comprises a display 18, for example LCD or LED,connected to the control circuit 9 which is configured to determine, bymeans of said display 18, a visualization of the selected operatingmode, of an indicative value of a maximum reached compression force, aswell as a confirmation of the outcome of the compression process.

According to one aspect of the invention, the method comprises a step ofcalculating (and possibly the display of) a residual number ofcompression or cutting cycles before a scheduled maintenance of thetool. Advantageously, the residual number of cycles is calculateddepending on:

a predetermined initial residual number of cycles,

stress values that are representative for and variable depending on themechanical stresses of the tool in the individual compression or cuttingcycles.

In one embodiment, the stress values are representative of the maximumcompression or cutting forces or for ranges of maximum compression orcutting forces, actually reached during each of the compression orcutting cycles, and the calculation of the residual number of cyclescomprises, for each cycle out of a sequence of consecutive cycles:

the calculation of a reduction value depending on the stress value ofthe current cycle wherein said reduction value is a variable quantityfrom one cycle to another depending on the maximum compression orcutting forces actually reached in the individual cycles,

the calculation of the number of cycles remaining after the completionof the current cycle by subtracting the reduction value from a residualnumber of cycles calculated for the cycle prior to the current cycle.

The calculation of the residual number of cycles may comprise thecalculation of a fraction of damage of at least one component of thetool (e.g. of the jaws) during each cycle depending on the stress value,for example using the following calculation method:

Step 1) Given the stress value pi reached in a given cycle, calculatingthe number of cycles Ni which a component of the tool (e.g. of the jaws)should perform to reach breaking point if it were stressed in each cyclewith the stress value pi, e.g. using the formula Ni=NR·(pR/pi)^(1/k)where NR and pR is a pair of known values (in particular a maximumstress and the number of cycles leading to breakage, applying at eachcycle a stress equal to the maximum stress; k is an experimental valueindicative of fatigue resistance of the tool).

Step 2) Calculating the fraction of fatigue damage of the component inthe cycle with stress pi, e.g. using the formula 1/δi=Ni,

Step 3) Calculating the reduction value, i.e. the number of adaptivecycles ni to subtract from the number of cycles until maintenance Nme.g. using the formula

Ni=δi·NR

where NR is the number of cycles leading to breakage of the componentwhen stressed in each cycle with the maximum stress pR.

Step 4) Calculating the number of cycles remaining until maintenance,e.g. using the formula

Nm(i)=Nm(i−1)−ni

where Nm (i−1) represents the residual number of cycles untilmaintenance in the previous cycle, and Nm (i) represents the residualnumber of cycles until maintenance in the current cycle.

To reduce the computational complexity, a series of predetermined rangesfor the stress values can be defined, with associated predeterminedreduction values and used instead of the full calculation fordetermining the reduction value depending on the stress value.

The method described can be performed by the electronic control circuit9 and the number of residual cycles can be shown for example by thedisplay 18 and/or an acoustic or visual signal may be generated by thecontrol circuit 9 by means of one or more signalling devices connectedthereto.

The control circuit 9 detects the stress value for each cycle using oneor more stress sensors, for example:

by detecting the pressure of the hydraulic fluid acting on the actuationpiston 12, using the pressure sensor 22 connected to the electroniccontrol circuit 9. In this case the stress value is the maximum pressureof the hydraulic fluid detected in the cycle.

detecting a force acting on the jaws, using a force sensor connected tothe electronic control circuit 9. In this case the stress value is themaximum force detected in the cycle.

detecting an indicative electrical quantity for the power absorbed bythe motor, using an electrical sensor 23 connected to the electroniccontrol circuit 9. In this case the stress value is the maximumelectrical quantity (e.g. electrical power or current) absorbed by themotor in the cycle.

The functioning of the tool 1 will be described below.

By pressing the actuation button 7 a micro switch of the control circuit9 is actuated, which starts the electric motor 6 and simultaneouslybegins to receive and process the signals indicative of the pressure ofthe hydraulic fluid detected by the pressure sensor 22. The controlcircuit 9 is configured so that the electric motor 6 remains switched ononly with the actuation button 7 pressed and is thus automaticallyswitched off with the release of said actuation button 7. When the jaws13, 14 reach the closed position, the control circuit 9 automaticallyswitches off the electric motor 6 before reaching the maximumcalibration pressure that would result in the automatic opening of thepressure relief valve 17. Now the actuation button 7 can be released.

For the return of the actuation piston 12 to its rest position (jawsopen), the tool 1 may comprise a member 20 for manual actuation or,alternatively, a means for automatic actuation of an outlet valve of thehydraulic fluid from the actuation cylinder into the tank.

The invention is applicable advantageously both to portable hydrodynamiccompression and/or cutting devices with a single housing and tohydrodynamic compression and/or cutting devices in which the hydraulicpump 11 can be separated and distanced from the compression and/orcutting head (actuation piston 12, jaws) and connected to it by aflexible hose 28 for pressurised oil (FIG. 13).

Obviously, a person skilled in the art may make further modificationsand variations to the compression and/or cutting tool according to thepresent invention so as to satisfy contingent and specific requirementswhile remaining within the scope of protection of the invention asdefined by the following claims.

1. A hydrodynamic compression or cutting tool, comprising: an electricmotor that can be powered by an electric power source, a hydrodynamicunit actuatable by the electric motor and suitable to carry out, inresponse to the movement of the motor, a pressure increase of ahydraulic liquid acting on an actuating piston so as to displace theactuating piston, two jaws connected to be movable to one another, atleast one movable jaw of which is connected to the actuating piston sothat, in response to the displacement of the actuating piston, the jawsperform a relative movement between an open position and a closedposition to carry out the compression or cut, an electronic controlsystem connected to the electric motor and to a user actuation memberfor actuating the electric motor, comprising an identification detectorin connection with the control circuit and suitable to detect anidentification characteristic: of the jaws, or of inserts received inthe jaws, or of an object to be compressed or cut.
 2. The tool accordingto claim 1, wherein the identification characteristic comprises a signalof a radio frequency identification tag (RFID-tag) of said objectintended to be compressed or cut.
 3. The tool according to claim 1,wherein the identification characteristic comprises a signal of a radiofrequency identification tag (RFID-tag) of the jaw.
 4. The toolaccording to claim 1, wherein the identification characteristiccomprises a signal of a radio frequency identification tag (RFID-tag) ofthe insert received in the jaws.
 5. The tool according to claim 1,wherein the identification characteristic comprises an optical orchromatic feature of an optical interface of the jaw or of the insert orof the object intended to be compressed or cut.
 6. The tool according toclaim 1, wherein the identification characteristic comprises a magneticfeature of the jaw or of the insert or of the object intended to becompressed or cut.
 7. The tool according to claim 1, wherein theidentification characteristic comprises an electrical feature of anelectric interface of the jaw or of the insert or of the object intendedto be compressed or cut.
 8. The tool according to claim 1, wherein theidentification characteristic comprises a shape feature of a mechanicalinterface of the jaw or of the insert or of the object intended to becompressed or cut.
 9. The tool according to claim 1, wherein theidentification detector is an object identification detector andcomprise a position sensor configured to detect a position of theactuation piston, wherein the electronic control circuit is in signalconnection with the pressure sensor, with the position sensor and withthe electric motor, and configured to identify an object engaged by thejaws depending on: the hydraulic fluid pressure detected by the pressuresensor and the position of the actuation piston detected by the positionsensor during actuation of the electric motor.
 10. A method foractuating a hydrodynamic compression tool, wherein said tool comprises:an electric motor powered by an accumulator; a hydrodynamic unitactuatable by the electric motor and suitable to carry out, in responseto the movement of the motor, a pressure increase of a hydraulic liquidacting on an actuating piston so as to displace the actuating piston;two jaws connected to be movable to one another, at least one movablejaw of which is connected to the actuating piston so that, in responseto the displacement of the actuating piston, the jaws perform a relativemovement between an open position and a closed position to carry out thecompression or cut, wherein said method comprises the steps of: bringingthe jaws close to one another by actuating the electric motor,identifying the type of object to be compressed or cut, performfunctions of the tool in dependency of the identified type of object.11. Method according to claim 10, comprising the step of detecting asignal of a radio frequency identification tag (RFID-tag) of said objectintended to be compressed or cut.
 12. Method according to claim 10,wherein said object identification is carried out automatically. 13.Method according to claim 12, wherein said object identification iscarried out by means of the steps: identifying, on the basis of themonitored pressure, an engagement moment in which the jaws engage theobject placed between them and in which the compression of the objectcommences, detecting a compression starting position of the actuationpiston at the moment of engagement, identifying the object engaged bythe jaws depending on the detected compression starting position. 14.Method according to claim 10, comprising the step of switching off theelectric motor depending on the type of object identified.
 15. Systemfor compressing or cutting objects, comprising: a hydrodynamiccompression or cutting tool comprising: an electric motor that can bepowered by an electric power source, a hydrodynamic unit actuatable bythe electric motor and suitable to carry out, in response to themovement of the motor, a pressure increase of a hydraulic liquid actingon an actuating piston so as to displace the actuating piston, two jawsconnected to be movable to one another, at least one movable jaw ofwhich is connected to the actuating piston so that, in response to thedisplacement of the actuating piston, the jaws perform a relativemovement between an open position and a closed position to carry out thecompression or cut, an electronic control system connected to theelectric motor and to a user actuation member for actuating the electricmotor, comprising an identification detector in connection with thecontrol circuit and suitable to detect an identification characteristic:of the jaws, or of inserts received in the jaws, or of an object to becompressed or cut, the system further comprising: an object intended tobe compressed or cut by using the hydrodynamic compression or cuttingtool, wherein said object to be compressed or cut comprises a radiofrequency identification tag (RFID-tag).
 16. System according to claim15, wherein said object is an electrical connector or a hydraulicconnector.